Back EMF Motor Controller

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https://robidouille.wordpress.com/2009/09/20/back-emf/

Calculations

  • At 10,000 rpm, each rotation takes 6 ms. If we have 10 magnets on an axial flux motor, then we have 0.6 ms over which to control the on-off of magnets. Since we need to divide that at least by 10, and more like 100 - so we need to have about 6-60 microsecond control over the turn-on of the signal.

Discussion

MJ to MD:

It doesn't look like the numbers are in our favor for back emf with arduino.

I'm getting about 6-60 microsecond response time control requirement as above.

How fast can we read and cycle through arduino code? I had an impression that once you're looping, it's like a ms per loop, so 10-100x slower than we need to read the back emf? Would be a sweet deal if we can do this, but it seems arduino is not fast enough, or it requires more insights onto the arduino operation to hack higher speeds, which is beyond me at this point.  I think the ESCs all use dedicated chips for back emf measurement, so they can do it in the required time?

So why does the [1] measurement work? It seems the motor is slower, not 10000 rpm as assumed for the 6-60 microsecond number.